An Izadi militia said it had wrested control of a section of the Iraqi-Syrian border area from Islamic State (ISIS / Daesh / ISIL / IS) militants southwest of Sinjar.

The YBS, whose forces are now based at the border village of Umm adh Dhiban, said it took the road west of the Sinjar mountain all the way to the Syrian border 13 days ago.

It says it will soon move towards the desert town of Ba'aj, an ISIS stronghold, along with the Popular Mobilization Forces (known as Hashd al-Shaabi, government-sanctioned Shiite militias) who in recent weeks have taken up positions in the desert west of Mosul.

Sinjar itself is controlled by the Peshmerga forces of the Kurdistan regional government.

The Peshmerga and the YBS maintain a frosty relationship.

The YBS is backed by the Kurdistan Workers' Party, better known as the PKK, a powerful Kurdish armed group whose branches extend into Turkey, Syria and Iraq.

It is also receiving support from the Iraqi government, which seeks to extend its power into an area that is largely under the influence of the Kurdish government's forces.

The operation is aimed at cutting the self-declared ISIS caliphate in two and making it impossible for the militants to move between the areas they control in Iraq and Syria.

It also illustrates the complexity of northern Iraqi politics where various armed groups and parties maneuver for influence, often caught between the Iraqi and Kurdish governments.